To simplify the assembly of electronic devices, electronic components are frequently furnished to manufacturers in the form of preassembled modules containing whole circuits for performing a given function. The modules can then be advantageously handled in the assembly line as single parts of a larger whole, substantially speeding and simplifying the overall assembly process.
Power supplies adapt well to this preassembled module concept. Manufacturers of electronic systems (such as computers and telephone switches) therefore commonly acquire power supplies as preassembled modules from third party suppliers, rather than build them themselves. To protect the components and interconnections within the preassembled modules from environmental and handling damage, and to render them easier to handle during the assembly process, the modules are frequently encapsulated (or "potted") prior to further assembly.
Power supplies have shrunk in size and grown in power-handling capability over the years. Unfortunately, the resulting increase in power-handling capacity per unit of circuit volume (power density) has made such power supplies evermore difficult to encapsulate.
In general, encapsulating electronic components that require substantial heat removal has proven to be an intransigent problem. Ordinary potting materials do not have a coefficient of thermal conductivity sufficient to accommodate some of today's high thermal density components. Potting materials that have a high coefficient of thermal conductivity tend to be too viscous, resulting in the formation of cavities in the material. Guaranteeing the absence of cavities requires substantial time and care, resulting in a marked (perhaps four-fold) increase in manufacturing time. Even given the extra time, encapsulating machines tend to jam in their attempts to manage the thicker material, forcing the assembly line to be interrupted so the machines can be cleaned and restarted.
Accordingly, what is needed in the art is an improved way to encapsulate power supplies and heat-producing electronic components in general.